Return-path: X-Andrew-Authenticated-as: 7997;andrew.cmu.edu;Ted Anderson Received: from hogtown.andrew.cmu.edu via trymail for +dist+/afs/andrew.cmu.edu/usr11/tm2b/space/space.dl@andrew.cmu.edu (->+dist+/afs/andrew.cmu.edu/usr11/tm2b/space/space.dl) (->ota+space.digests) ID ; Fri, 1 Feb 91 01:36:49 -0500 (EST) Message-ID: <0beElwO00WBw45ak5b@andrew.cmu.edu> Precedence: junk Reply-To: space+@Andrew.CMU.EDU From: space-request+@Andrew.CMU.EDU To: space+@Andrew.CMU.EDU Date: Fri, 1 Feb 91 01:36:44 -0500 (EST) Subject: SPACE Digest V13 #096 SPACE Digest Volume 13 : Issue 96 Today's Topics: Asteroid Near Miss Schools Galileo Update - 01/25/91 Redundancy vs reliability * SpaceNews 28-Jan-91 * POTENTIAL GEOMAGNETIC STORM WARNING Administrivia: Submissions to the SPACE Digest/sci.space should be mailed to space+@andrew.cmu.edu. Other mail, esp. [un]subscription requests, should be sent to space-request+@andrew.cmu.edu, or, if urgent, to tm2b+@andrew.cmu.edu ---------------------------------------------------------------------- Date: 25 Jan 91 21:18:05 GMT From: swrinde!elroy.jpl.nasa.gov!jato!mars.jpl.nasa.gov!baalke@ucsd.edu (Ron Baalke) Subject: Asteroid Near Miss New York Times -- 1/25/91 "Astronomers Duck as a Tiny Asteroid Passes" By John Wilford "Astronomers scanning the sky a week ago were astonished to see a small asteroid streaking by Earth, within less than half the distance to the Moon. It was the smallest, closest asteroid ever observed passing safely by Earth." The story says the observations were made last Thursday night and Friday morning by members of the Spacewatch team from the University of Arizona. The paper explains that Spacewatch is a regular vigil of tracking asteroids that may be coming perilously close to Earth and uses sophisticated and sensitive electronic detectors. The story cites the Spacewatch chief astronomer, Dr. Tom Gehrels, and his belief that the asteroid in question would not visit the vicinity of Earth again, but rather was tied to the gravity field of Venus and likely would eventually enter into Venus' atmosphere. The Times says this asteroid was estimated to be about 30 feet in diameter and came within 106,000 miles of the Earth and that the previous closest call was from an asteroid of about a half-mile in diameter which passed within 500,000 miles of earth in March 1989. ___ _____ ___ /_ /| /____/ \ /_ /| Ron Baalke | baalke@mars.jpl.nasa.gov | | | | __ \ /| | | | Jet Propulsion Lab | ___| | | | |__) |/ | | |___ M/S 301-355 | It's 10PM, do you know /___| | | | ___/ | |/__ /| Pasadena, CA 91109 | where your spacecraft is? |_____|/ |_|/ |_____|/ | We do! ------------------------------ Date: 25 Jan 91 20:03:12 GMT From: prism!hamlet!bcomisky@gatech.edu (William J. Comisky) Subject: Schools I was wondering which schools are acknowledged as having the best astronomy and/or astrophysics programs, both graduate and undergraduate . . . Anyone? -- William J. Comisky (GTRI/STL/MSD) (404) 528-7xxx Georgia Institute of Technology, Atlanta Georgia, 30332 uucp: ...!{allegra,amd,hplabs,ut-ngp}!gatech!msd!bcomisky Internet: bcomisky@msd.gatech.edu ------------------------------ Date: 26 Jan 91 00:00:38 GMT From: sdd.hp.com!elroy.jpl.nasa.gov!jato!mars.jpl.nasa.gov!baalke@ucsd.edu (Ron Baalke) Subject: Galileo Update - 01/25/91 GALILEO STATUS REPORT January 25, 1991 The status of the Galileo spacecraft status as of end of day January 24 was as follows: o System Power Margin - 69 watts o Spin Configuration - All-Spin - cruise mode o Spin Rate/Sensor - 2.89rpm/star scanner o Spacecraft Attitude Sun Point Angle - approximately 1.5 degrees plus or minus 0.3 degree o Downlink telemetry rate/antenna - 40 bits/second (uncoded)/LGA-2 (Low Gain Antenna-2) o General Thermal Control - all temperatures within acceptable range o RPM (Retro Propulsion Module) Tank Pressures - all within acceptable range Today, the spacecraft successfully completed the planned sun acquisition and RPM maintenance activities. Later today a cruise science memory readout will be performed for the MAG (Magnetometer) and DDS (Dust Detector) instruments. Weekend operations will be limited to a routine USO (Ultra Stable Oscillator) characterization test on Saturday and a planned sun acquisition on Sunday. A total of 3080 real-time commands have been transmitted to Galileo. Of these, 1687 have been pre-planned in the sequence design and 1393 were not. In the past week, a total of 130 real-time commands were sent; all were pre-planned. ___ _____ ___ /_ /| /____/ \ /_ /| Ron Baalke | baalke@mars.jpl.nasa.gov | | | | __ \ /| | | | Jet Propulsion Lab | ___| | | | |__) |/ | | |___ M/S 301-355 | It's 10PM, do you know /___| | | | ___/ | |/__ /| Pasadena, CA 91109 | where your spacecraft is? |_____|/ |_|/ |_____|/ | We do! ------------------------------ Date: Sun, 27 Jan 91 02:00:08 EST From: John Roberts Disclaimer: Opinions expressed are those of the sender and do not reflect NIST policy or agreement. Subject: Redundancy vs reliability >From: v071pzp4@ubvmsd.cc.buffalo.edu (Craig L Cole) >Newsgroups: sci.space >Subject: Re: Why man rate? (was: space news from Dec 17 AW&ST) >Date: 25 Jan 91 16:54:43 GMT >Organization: University at Buffalo >Sure, adding safety and redudancy features increases the complexity >of the system, which in actually starts to reduce safety. This is not a proper interpretation of the proper use of redundancy. The only reason to add redundancy is to increase reliability, and to go beyond this to a point at which overall reliability is actually decreased would be pretty idiotic. Yes, determining the point of optimum redundancy an setting up interfaces, control, and switching systems so that you do not add other problems is a challenge, but I believe that it is within the ability of the designers of the Shuttle and other US aerospace systems. The actual optimum choice can not be made by use of "common sense", and there is no simple general rule of thumb - extensive calculations and simulations are required for every design decision. In the past, I have had long arguments with individuals over the premise that it is theoretically possible to build an advanced system such as a military aircraft with redundant components such that overall system reliability is improved even though the (hopefully) statistically independent component failure rate increases. For some reason this concept (admittedly somewhat subtle) seems to be beyond the ability of a large portion of the population, but recent events involving military aircraft suggest that it is a valid design approach, even beyond the expectations of the proponents. Unfortunately, it is also generally the case that high-reliability redundant systems are more expensive than simpler systems. The Shuttle, for example, is a reliable but very expensive system. It's the cost, rather than the reliability issues, that show it's time to look for substitutes for the necessary functions the Shuttle provides. With luck, the current fleet may last until such substitutes are available. (Though it's probably a sensible precaution to keep the capability for *one* more replacement vehicle if needed.) >But, after >seeing all of the glitches the shuttle has usually easily solved >by these features, I'd rather take my chances having those extra >systems to use. >Man-rating a rocket will eventually become an outdated term, as rockets >will become inherently be safe enough to launch whatever you want -- >satellites, manned capsules, or whatever. Well, there are other considerations besides reliability - such as peak acceleration and vibration, which might not affect a given inanimate payload, but which would affect humans. It's unlikely that the Sprint missile will ever be man-rated (100G takeoff (!)). >Craig Cole >V071PZP4@UBMVS.BITNET >V071PZP4@UBVMS.CC.BUFFALO.EDU John Roberts roberts@cmr.ncsl.nist.gov ------------------------------ Date: 26 Jan 91 03:47:54 GMT From: ka2qhd!kd2bd@rutgers.edu (John Magliacane) Subject: * SpaceNews 28-Jan-91 * SB SPACE @ ALLBBS < KD2BD $SPC0128 * SpaceNews 28-Jan-91 * Bulletin ID: $SPC0128 ========= SpaceNews ========= MONDAY JANUARY 28, 1991 SpaceNews originates at KD2BD in Wall Township, New Jersey, USA. It is published every week and is made available for unlimited distribution. * U2MIR-1 NEWS * ================ Packet Radio (AX.25) communications were carried out last week between the Soviet "Mir" space station and many ground stations on 145.550 MHz. Callsigns of U2MIR and U2MIR-1 were used by the amateur radio station on board Mir. Personal observations as well as observations by others seem to confirm the fact that Mir now has a fully operational packet radio bulletin board system, complete with a "standard" PBBS command system capable of supporting mail exchanges between users as well as disseminating news bulletins to all users of the system. The U2MIR-1 BBS system is compatible with standard 1200 baud 2-meter FM packet stations currently in existance all over the world. No special TNCs or external PSK modems are required for access. Downlink signals from Mir are strong. Even operation with indoor antennas seems possible. Packet radio operations from Mir came as quite a surprise to many who expected operations to begin in March. While BBS operations took place for several days last week, it remains to be seen when or if operations will continue on a permanent basis. Packet BBS operations from U2MIR can generally be made at any time, since the station can be run in an unattended mode while the cosmonauts are sleeping or busy with other work. * SPACE RADIATION * =================== NASA is reporting that operations of the orbiting Hubble Space Telescope are being affected by radiation induced electronic failures on a daily basis. Single event upsets (SEUs) in a 1 kilobit low-power TTL bipolar random access memory (93L-422) are causing Hubble's crucial focusing elements to lose data on a regular basis. SEU induced errors are being minimized by using a rapid refresh cycle with the RAM device to limit the time in which multiple SEUs can occur. The 93L-422 RAM device has a well documented history of SEU failures, but was used anyway since clever software routines could help correct or prevent SEUs from affecting telescope operations. It appears the SEU problem was greater than anticipated and might also explain why NASA scientists mysteriously lost radio contact with the Magellan Venus spacecraft for 18 hours shortly after insertion motor separation last fall. Scientists are now trying to duplicate that problem in an effort to determine its cause. All OSCAR satellites experience problems with radiation induced RAM errors. High energy radiation particles damaged one of the sense amplifiers in the Integrated Housekeeping Unit (IHU) on board OSCAR-10. Since that damage occurred, the spacecraft essentially became "brain dead", and no longer transmits RTTY and CW telemetry or supports a sophisticated transponder schedule. Most satellites operating with 8-bit CPUs generally use 12-bit RAM systems to help reduce the effect of radiation induced memory errors. OSCAR-11 as well as the MicroSats run a "wash" routine as part of eir spacecraft's operating system. The wash routine checks all memoryocations, counting all errors and correcting all single bit errors. A "wash pointer" reports the current memory address checked and transmits thanformation as part of the spacecraft telemetry report. OSCAR-11 has been used quite extensively to study the problem of single event upsets on spacecraft systems. In fact, it is an interesting hobby to find correlations between radiation induced spacecraft RAM errors, space dust counts, and ionospheric HF radio propagation conditions! Most SEUs occur around the polar regions of the Earth, especially around an area known as the "South Atlantic Anomaly", a heavily proton charged region around Antartica. Solar flares are also responsible for increasing the rate at which SEUs occur in satellite computer subsystems. * TNX QSL! * ============ A special thanks to all those who sent QSLs and letters to SpaceNews: N1HZH : Joel Magid, Groton, Massachusettes, USA K3CRF : Dave Smith, Bellevue, Nebraska, USA ...and e-mail messages: VK2EE, WB2DHY, WB4IJV, K7EA, DG9MAQ * FEEDBACK WELCOMED * ===================== Feedback regarding SpaceNews can be directed to the editor (John) via any of the following paths: INTERNET : kd2bd@ka2qhd.de.com PACKET : KD2BD @ NN2Z.NJ.USA.NA UUCP : ...uunet!rutgers!ka2qhd!kd2bd MAIL : John A. Magliacane, KD2BD Department of Electronics Technology Advanced Technology Center Brookdale Community College 765 Newman Springs Road Lincroft, New Jersey 07738 U.S.A. /EX -- John A. Magliacane FAX : (908) 747-7107 Electronics Technology Department AMPR : KD2BD @ NN2Z.NJ.USA.NA Brookdale Community College UUCP : ...!rutgers!ka2qhd!kd2bd Lincroft, NJ 07738 USA VOICE: (908) 842-1900 ext 607 ------------------------------ X-Delivery-Notice: SMTP MAIL FROM does not correspond to sender. Date: Sun, 27 Jan 91 13:15:30 MST From: std_oler%HG.ULeth.CA@vma.cc.cmu.edu (Cary Oler) Subject: POTENTIAL GEOMAGNETIC STORM WARNING X-St-Vmsmail-To: st%"space+@andrew.cmu.edu" ********************************************* *** POTENTIAL GEOMAGNETIC STORM WARNING *** ********************************************* Issued: 18:00 UT, 27 January Geomagnetic Storm Warning ------------- Attention: Due to the recent major flaring and expected interplanetary shocks, a Potential Geomagnetic Storm Warning has been issued, particularly for the middle and high latitude regions. There is uncertainty regarding how intense the geomagnetic activity could become. Hence, a geomagnetic storm warning has been issued. Please note that this warning does not mean that a magnetic storm is in progress. This warning is meant only to alert those who could be affected to the potential for geomagnetic storming. Activity is currently expected to remain near active to very active levels for middle latitudes, but higher latitudes could sustain minor storming for extended periods. If geomagnetic storming does develope over middle latitudes, a Geomagnetic Storm Alert will be posted. The estimated planetary magnetic A-index for the next three days is expected to be near 25. High latitudes could experience magnetic storming capable of pushing the A-index above 50. Middle latitudes will likely experience activity between 20 and 35. Low latitudes will likely observe A-index values of near 15 to possibly 30. Conditions should begin to improve on 30 January (possibly earlier), barring any further major flaring (which seems likely at the present time). Watch for possible geomagnetic and/or major flare alerts. ** End of Warning ** ------------------------------ End of SPACE Digest V13 #096 *******************